Generation of Airborne Multi-Walled Carbon Nanotubes for Inhalation Studies

Recent studies suggest that inhaled or intratracheally instilled multi-walled carbon nanotubes (MWCNTs) cause adverse health effects depending on the fiber length. In the present study a simple batch particle generation system was developed to generate airborne MWCNTs for inhalational toxicology studies. The generation rate can be controlled by the amplitude of sieve shaker. Maximum concentration of respirable airborne MWCNTs was 1.2 mg m^–3 at a nose-exposure chamber supplied with air at flow rate of 30 L min^–1. We examined the performance of airborne MWCNT generation system and characterized properties of generated fibrous particles at mass concentrations of 0.4 mg m^–3 (particle number; ca. 1700 cm^–3). Monomodal shaped size distributions with peak located at electrical mobility diameter of 300 nm (in number) and aerodynamic diameter of 1–2 μm (in mass) were measured with a scanning mobility particle sizer and with a low-pressure impactor, respectively. Two hour particle generation reproducibility tests were conducted five times, in which stability and repeatability of particle size and total number concentration were within an acceptable range. Aerodynamically classified particle morphology was studied by TEM, dissociated fiber-like and agglomerated MWCNT particles were observed. The former contributes up to 38% to counted particles, and the average width and length of fiber were 80 nm and 3.7 μm, respectively, with an aerodynamic size for particle of 260–381 nm.